An arrangement of this type is known from U.S. Pat. No. 5,784,207 What is known as an eyepiece cup is arranged longitudinally displaceably on an eyepiece housing, in order for it to be possible for glasses-wearers and normal-sighted observers to set an optimum position of the eye in relation to the exit pupil of the eyepiece. A screw is attached to the eyepiece housing, the head of which is guided in a groove which is in the inner wall of the eyepiece cup. By rotating the eyepiece cup, the height of the eyepiece cup is adjusted relative to the eyepiece housing. Provided opposite the groove-guide in the cross section of the arrangement, between the eyepiece cup and the eyepiece housing, is a catch arrangement for different extension positions of the eyepiece cup. The catch arrangement consists of a plate spring element which is provided with a nose and is arranged on the eyepiece housing, the nose engaging in appropriately shaped notches in the inner wall of the eyepiece cup.
The large number of parts makes assembly more difficult and is expensive. The resilience of the catching element wears out as a result of material fatigue. Demounting of the eyepiece cup for cleaning purposes is not envisaged.
An eyepiece housing with an adjustable, in particular asymmetrically shaped eyepiece cup is known from DE 299 04 366 U1. A guide, which likewise consists of a groove and a pin, is intended to ensure that the eyepiece cup is stopped in the displacement end positions concerned and always has the same orientation in the circumferential direction. To this end, catching positions are provided, which are arranged on a line parallel to the longitudinal axis of the eyepiece housing. As the guide groove is inclined in relation to the longitudinal axis, its direction always has to be diverted, in relation to the designated line parallel to the longitudinal axis, for passage into the catching position. The catching is brought about by an angular change in direction of the guide groove.
While it is true that this guide manages without additional moving parts, it nevertheless requires a relatively complex shape of the guide tracks, which can wear at the angular diversions to the catch position when used for a relatively long time. Demounting of the eyepiece cup is not envisaged in this case either.
It is therefore an object of the invention to provide a simple and cost-effective fastening, guidance and catching arrangement for an eyepiece cup to be adjusted rotatably on an eyepiece housing, which manages with only one moving mechanical component which is non-sensitive to environmental influences and, for cleaning, can be removed from the eyepiece housing, cleaned and replaced rapidly and without additional tools.